1. Field of the Invention
The present invention relates to a damper, and more particularly, to a controllable magneto-rheological fluid damper.
2. Discussion of the Related Art
During the past decade, there has been increasing interest in the development of controllable shock absorbers that utilize electro-rheological fluid (ERF) and magneto-rheological fluid (MRF). The possibility of using ERF or MRF based damping devices in various applications has made these controllable devices attractive to the vibration control field. Controllable shock absorbers can potentially be used in a variety of mechanical systems such as bicycles, motorcycles, automobiles, trucks, ships, trains, airplanes, bridges, buildings and/or other structures, sports equipment and any other systems using vibration control.
An MRF consists of micron-sized, magnetically polarized particles suspended in a carrier fluid such as silicon or mineral oils. MRFs are capable of responding to a magnetic field in a few milliseconds. The material properties of an MRF can be changed rapidly by increasing or decreasing the intensity of the applied magnetic field. This is realized as a controllable increase in the apparent viscosity of the fluid by varying the current supplied to the damper""s built-in electromagnet. A higher fluid viscosity yields a higher damping force. This is the mechanism behind the controllability of MRF dampers.
In a conventional MRF damper disclosed by FIG. 9(c) of U.S. Pat. No. 5,277,281, the system uses an entrance fluid port and a exit fluid port connected by a channel. The fluid flows through a lateral channel portion in the path between the entrance and exit ports. Here, the lateral channel portion extends through a fixed arc. In addition, the lateral channel is required to flow around a plug, associated with the shaft, that extends into the center of the piston.
As a result of this design, the above-referenced damper suffers from a number of limitations. For example, the damper cannot accommodate multiple entrance and exit ports. The use of a single entrance and a single exit port diminishes the flexibility of the design with respect to the damping force that can be generated. This is of particular importance when small initial or zero-field (no current applied) damping forces are desired. In addition, the MR fluid must flow around the plug in the center of the piston, thereby reducing the surface area to which the MR fluid chains adhere to the wall. This reduction in surface area reduces the damping force that can be generated by the MR fluid upon application of a magnetic field.
Accordingly, the present invention is directed to a damper that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a damper that has improved damping characteristics.
Another object of the present invention is to provide of a damper that can be efficiently manufactured at a low cost.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a damper comprises a housing; a piston movably disposed within the housing, the piston dividing an interior of the housing into first and second cavities and having a passage defined in the piston to couple the first and second cavities, wherein the passage includes at least a disk shape space within the piston defined between by two substantially parallel surfaces; a magneto-rheological (MR) fluid contained within at least the first cavity, motion of the piston being damped by a flow of MR fluid through the passage; a magnet disposed to produce a magnetic field within at least the disk shape space of the passage.
In another aspect, a damper comprises a housing; a piston movably disposed within the housing, the piston dividing an interior of the housing into first and second cavities and having a passage defined in the piston to couple the first and second cavities, wherein the passage includes at least a space within the piston coupled with the first cavity through a plurality of inlet flow ports and coupled with the second cavity through at least one outlet flow port; a magneto-rheological (MR) fluid contained within at least the first cavity, motion of the piston being damped by a flow of MR fluid through the passage; a magnet disposed to produce a magnetic field within at a portion of the passage.
In another aspect, a damper comprises a housing; a piston movably disposed within the housing, the piston dividing an interior of the housing into first and second cavities and having a passage defined in the piston to couple the first and second cavities, wherein the passage includes a plurality of inlet ports to couple the passage with the first cavity and a plurality of outlet ports to couple the passage with the second cavity, the number of inlet flow ports being different than the number of outlet flow ports; a magneto-rheological (MR) fluid contained within at least the first cavity, motion of the piston being damped by a flow of MR fluid through the passage; a magnet disposed to produce a magnetic field within at least a portion of the passage.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.